Center for Asthma Prevention and Education of Capital Institute of Pediatrics investigated the national asthma prevalence in 900 thousands children in 27 provinces and cities, which average rate was 0.11% to 2.03% in 1990. In 2000, we investigated it again in 31 provinces(43 cities) and the average national children asthma prevalence rate was 1.97%(0.25% to 4.63%) which was much higher than that in 1990.